Technical Field
The present subject matter relates to an apparatus for measuring the position of a vehicle or a surface thereof on a roadway.
Background Art
The measurement of the position of vehicles is important for many tasks in the field of traffic control, traffic monitoring and traffic billing, for example in order to determine the lane used by a vehicle at an electronic traffic control point or tollbooth or also in order to identify the longitudinal position of a vehicle along the roadway so as to be able to assign the vehicle unambiguously to the image of a traffic monitoring camera. The measurement of the position of a surface of the vehicle, for example the roof or side faces thereof, is of significance in order to determine the size of the vehicle and therefore classify said vehicle, for example in order to determine whether the vehicle is a passenger vehicle or lorry, for example so as to be able to check and enforce traffic restrictions or toll fees dependent on vehicle class.
Predominantly optical systems, such as laser scanners or video cameras, are currently used for position measurement. These systems are reliant on good visibility and are therefore highly dependent on the weather; they often fail in rain, snow or spray. The optics of laser scanners and video cameras also requires frequent cleaning in order to remain ready for use, and these systems have a limited service life and a limited temperature range due to mechanically moved parts.
In sub-areas such as traffic flow monitor systems, radar systems are also currently used which, from a raised point, for example an antenna mast next to a motorway, detect moved vehicles by means of Doppler radar and can track the movement of said vehicles in a radar image. The accuracy of the position measurement of such radar systems is limited, and the Doppler evaluation of the vehicle speeds requires a high processing effort in order to create the traffic flow image.